Grinding machines have been utilized to finish developed parts for subsequent use in mechanical and other mechanisms. The purpose of the grinding machine is to finish the developed surface of a part, typically metal, so as to provide for the necessary shape and dimensions thereof. Examples of developed parts include a hydraulic device valve as disclosed in the U.S. Pat. No. 5,173,043 entitled REDUCED SIZE HYDRAULIC MOTOR, and the rotor as disclosed in the U.S. Pat. No. 4,357,133 entitled ROTARY GEROTOR HYDRAULIC DEVICE WITH FLUID CONTROL PASSAGEWAYS THROUGH THE ROTOR. Taking the hydraulic motor rotor as an example, the outer surface of this rotor has a generated developed surface, which surface must be tightly controlled in order to cooperate with the rolls of the surrounding stator in order to provide for a volumetrically and mechanically efficient gerotor mechanism. The grinding of this outer surface allows for the developing and maintaining of tighter spacing and tolerances between the rotor and surrounding stator, thus also maintaining tighter quality control between successive units.